1. Field of the Invention
The invention relates in general to elevator systems, and more specifically to new and improved apparatus and methods for determining the proper direction to a target floor when an elevator car overshoots or undershoots the floor and stops outside the normal landing zone.
2. Description of the Prior Art
An elevator car, when stopping at a floor, usually stops within a predetermined landing zone. Once the car is within this zone, it will stop within about 0.25 inch of floor level, and any stretch-of-rope releveling required will automatically take place, to maintain the desired level position. Hatch transducers, leveling switches, and the like, are used to establish the proper car travel direction when car movement or releveling is necessary within the landing zone.
If an elevator car overshoots or undershoots the landing zone of a target floor, for some reason, such as due to an error in the position transducer which maintains car position, the floor selector will indicate that the car is at the floor. Unless the elevator system is of the type which maintains absolute car position at all times, such as from a coded tape in the hoistway and a tape reader on the car, the proper travel direction to level the car will not be known. In this situation, the elevator car may be placed into a reset mode in which the car will be assigned an arbitrary, predetermined travel direction. The car may then proceed to the terminal floor in the selected direction, to reset the floor selector, or it may travel to the closest floor in the selected travel direction, if the car position for selector resetting purposes can be obtained from each floor. In any event, a landing error in which the car lands outside the landing zone disrupts normal elevator service until a selector reset mode has resynchronized the selector.